Circulating inflammatory cytokines and the risk of sepsis: a bidirectional mendelian randomization analysis

BACKGROUND

Sepsis is a life-threatening condition that is characterized by multiorgan dysfunction and caused by dysregulated cytokine networks, which are closely associated with sepsis progression and outcomes. However, currently available treatment strategies that target cytokines have failed. Thus, this study aimed to investigate the interplay between genetically predicted circulating concentrations of cytokines and the outcomes of sepsis and to identify potential targets for sepsis treatment.

METHODS

Data related to 35 circulating cytokines in 31,112 individuals (including 11,643 patients with sepsis) were included in genome-wide association studies (GWASs) from the UK Biobank and FinnGen consortia. A bidirectional two-sample Mendelian randomization (MR) analysis was performed using single nucleotide polymorphisms (SNPs) to evaluate the causal effects of circulating cytokines on sepsis outcomes and other cytokines.

RESULTS

A total of 35 inflammatory cytokine genes were identified in the GWASs, and 11 cytokines, including Interleukin-1 receptor antagonist (IL-1ra), macrophage inflammatory protein 1 (MIP1α), IL-16, et al., were associated with sepsis outcome pairs according to the selection criteria of the cis-pQTL instrument. Multiple MR methods verified that genetically predicted high circulating levels of IL-1ra or MIP1α were negatively correlated with genetic susceptibility to risk of sepsis, including sepsis (28-day mortality), septicaemia, streptococcal and pneumonia-derived septicaemia (P ≤ 0.01). Furthermore, genetic susceptibility of sepsis outcomes except sepsis (28-day mortality) markedly associated with the circulating levels of five cytokines, including active plasminogen activator inhibitor (PAI), interleukin 7 (IL-7), tumour necrosis factor alpha (TNF-α), beta nerve growth factor (NGF-β), hepatic growth factor (HGF) (P < 0.05). Finally, we observed that the causal interaction network between MIP1α or IL-1ra and other cytokines (P < 0.05).

CONCLUSIONS

This comprehensive MR analysis provides insights into the potential causal mechanisms that link key cytokines, particularly MIP1α, with risk of sepsis, and the findings suggest that targeting MIP1α may be a potential strategy for preventing sepsis.

Integrated mRNA-miRNA transcriptome profiling of blood immune responses potentially related to pulmonary fibrosis in forest musk deer

Background

Forest musk deer (FMD, Moschus Berezovskii) is a critically endangered species world-widely, the death of which can be caused by pulmonary disease in the farm. Pulmonary fibrosis (PF) was a huge threat to the health and survival of captive FMD. MicroRNAs (miRNAs) and messenger RNAs (mRNAs) have been involved in the regulation of immune genes and disease development. However, the regulatory profiles of mRNAs and miRNAs involved in immune regulation of FMD are unclear.

Methods

In this study, mRNA-seq and miRNA-seq in blood were performed to constructed coexpression regulatory networks between PF and healthy groups of FMD. The hub immune- and apoptosis-related genes in the PF blood of FMD were explored through Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Further, protein-protein interaction (PPI) network of immune-associated and apoptosis-associated key signaling pathways were constructed based on mRNA-miRNA in the PF blood of the FMD. Immune hub DEGs and immune hub DEmiRNAs were selected for experimental verification using RT-qPCR.

Results

A total of 2744 differentially expressed genes (DEGs) and 356 differentially expressed miRNAs (DEmiRNAs) were identified in the PF blood group compared to the healthy blood group. Among them, 42 DEmiRNAs were negatively correlated with 20 immune DEGs from a total of 57 correlations. The DEGs were significantly associated with pathways related to CD molecules, immune disease, immune system, cytokine receptors, T cell receptor signaling pathway, Th1 and Th2 cell differentiation, cytokine-cytokine receptor interaction, intestinal immune network for IgA production, and NOD-like receptor signaling pathway. There were 240 immune-related DEGs, in which 186 immune-related DEGs were up-regulated and 54 immune-related DEGs were down-regulated. In the protein-protein interaction (PPI) analysis of immune-related signaling pathway, TYK2, TLR2, TLR4, IL18, CSF1, CXCL13, LCK, ITGB2, PIK3CB, HCK, CD40, CD86, CCL3, CCR7, IL2RA, TLR3, and IL4R were identified as the hub immune genes. The mRNA-miRNA coregulation analysis showed that let-7d, miR-324-3p, miR-760, miR-185, miR-149, miR-149-5p, and miR-1842-5p are key miRNAs that target DEGs involved in immune disease, immune system and immunoregulation.

Conclusion

The development and occurrence of PF were significantly influenced by the immune-related and apoptosis-related genes present in PF blood. mRNAs and miRNAs associated with the development and occurrence of PF in the FMD.

Protective role of the novel cytokine Metrnl/ interleukin-41 in host immunity defense during sepsis by promoting macrophage recruitment and modulating Treg/Th17 immune cell balance

BACKGROUND

Metrnl play an immunocytokine-like role in several diseases, which is also known as meteorin-like because it is homologous to the neurotrophic factor meteorin (Metrn). Although the expression and function of Metrnl, including neurotrophic, immunomodulatory, and insulin resistance functions in different tissues have been extensively studied, its role in sepsis has remained largely limited.

METHODS

The present work analyzed the levels of Metrnl and cytokines in the circulation, such as tumor necrosis factor (TNF-α), interleukin (IL-1)β, IL-6, IL-8, together with IL-10 among septic adult patients. Clinical information was obtained from such patients, including sofa score, procalcitonin(PCT)count, and C-reactive count (CRP) within 24 h when entering the intensive care unit (ICU). We constructed a sepsis model in Metrnl-deficient or normal wild-type mice using cecal ligation and perforation to study its functions in bacterial burden, survival, cytokine/chemokine generation, peritoneal lavage fluid neutrophils, macrophage and lymphocyte recruitment, and Treg/Th17 immune cell balance after CLP-induced sepsis.

RESULTS

The expression of Metrnl was remarkably elevated in the early phase of sepsis clinically. Its serum content in patients dying of sepsis slightly decreased relative to that in survivors. Furthermore, the concentration of Metrnl in septic cases when entering the ICU independently predicted the 28-day mortality. For septic patients who had low serum Metrnl content (≤ 274.40 pg/mL), the death risk increased by 2.3 folds relative to those who had a high serum content. It is reported that Metrnl is probably insufficient among patients dying of sepsis. Additionally, the content of Metrnl in the serum of septic patients when entering the ICU is markedly and negatively related to the levels of TNF-α, IL-1β, IL-6, IL-8, IL-17, PCT, and Sofa score. Collectively, Metrnl could be a potential therapeutic target for sepsis. A low-lethality non-severe sepsis (NSS) model was constructed, which suggested that Metrnl insufficiency elevated the death rate and reduced bacterial clearance during sepsis. For Metrnl-deficient mice, impaired sepsis immunity defense might be related to decreased macrophage recruitment and Treg/Th17 lymphocyte imbalance. Recombinant Metrnl administered to Metrnl-deficient mice abolished the immunity defense impairment following NSS while protecting the high-lethality severe sepsis (SS) model in wild-type (WT) mice. In addition, Metrnl-induced sepsis prevention was intricately associated with the increased recruitment of peritoneal macrophages and modulation of the Treg/TH17 immune cell balance. Furthermore, CCL3 exposure in Metrnl-deficient mice reduced peritoneal bacterial loads while improving survival during sepsis partially by promoting the recruitment of peritoneal macrophages. Furthermore, Metrnl regulated the polarization of M1 macrophages through the ROS signaling pathway and promoted macrophage phagocytosis, thereby killing Escherichia coli.

CONCLUSIONS

The present proof-of-concept work suggests that Metrnl-mediated recruitment of macrophages significantly affects sepsis defense in the host and modulates the Treg/Th17 immune cell balance. Findings in this work shed more light on the development of host-directed treatments that can be used to manipulate host immunity to treat sepsis.

The role of the glucocorticoid receptor and its impact on steroid response in moderate-severe COVID-19 patients

The effect of corticosteroid therapy in COVID-19 patients is mediated by its suppressive effect on the regulations of inflammatory response. However, its clinical outcome is often unpredictable. This study aimed to explore the role of glucocorticoid receptors in corticosteroid response in Moderate-Severe COVID-19 patients. In this cross-sectional study, we attempted to find the relationship between the expression of the glucocorticoid receptor (encoded by NR3C1), the variation of glucocorticoid receptors isoform, and the mutations of glucocorticoid receptors exon with clinical response to corticosteroids. In addition, the relationship between glucocorticoid receptors expression and the expression of IκBα (encoded by NFKBIA) and glucocorticoid-induced leucine zipper protein (GILZ; encoded by TSC22D3) as steroid pathways was also evaluated. Thirty-four COVID-19 patients were studied. Blood was drawn before and on day 5 of corticosteroid treatment. Glucocorticoid receptors expression, isoform, and mutation were determined by RNA sequencing from white blood cells. Based on the improvement of clinical and oxygen status, patients were classified into responder and non-responder groups. Of thirty-four patients, 23 (67.6%) showed excellent responses to corticosteroids, and 11 (32.4%) were non-responders. The NR3C1 gene expression was significantly higher in the responsive group at baseline and after five days of glucocorticoid treatment. Isoform variant and mutation of glucocorticoid receptors did not correlate with clinical response. The expression of IκBα and GILZ correlated positively with glucocorticoid receptors expression. This study elucidates the relationship between glucocorticoid receptor expression with therapeutic responses to corticosteroids in moderate-severe COVID-19.

The C-C Chemokine Receptor Type 4 Is an Immunomodulatory Target of Hydroxychloroquine

The emergence of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; COVID-19) in China, reported to the World Health Organization on December 31, 2019, has led to a large global pandemic and is a major public health issue. As a result, there are more than 200 clinical trials of COVID-19 treatments or vaccines that are either ongoing or recruiting patients. One potential therapy that has garnered international attention is hydroxychloroquine; a potent immunomodulatory agent FDA-approved for the treatment of numerous inflammatory and autoimmune conditions, including malaria, lupus, and rheumatoid arthritis. Hydroxychloroquine has demonstrated promise in vitro and is currently under investigation in clinical trials for the treatment of COVID-19. Despite an abundance of empirical data, the mechanism(s) involved in the immunomodulatory activity of hydroxychloroquine have not been characterized. Using the unbiased chemical similarity ensemble approach (SEA), we identified C-C chemokine receptor type 4 (CCR4) as an immunomodulatory target of hydroxychloroquine. The crystal structure of CCR4 was selected for molecular docking studies using the SwissDock modeling software. In silico, hydroxychloroquine interacts with Thr-189 within the CCR4 active site, presumably blocking endogenous ligand binding. However, the CCR4 antagonists compound 18a and K777 outperformed hydroxychloroquine in silico, demonstrating energetically favorable binding characteristics. Hydroxychloroquine may subject COVID-19 patients to QT-prolongation, increasing the risk of sudden cardiac death. The FDA-approved CCR4 antagonist mogalizumab is not known to increase the risk of QT prolongation and may serve as a viable alternative to hydroxychloroquine. Results from this report introduce additional FDA-approved drugs that warrant investigation for therapeutic use in the treatment of COVID-19.